What is darkness

[Brian W]

This question was raised in a light hearted fashion on another site but it has intrigued me. Is darkness merely the absence of light or is it actually 'something'?
Brian:help:

[leon]

Brian, I am no expert but I reckon when one blows out the Sun so to speak, you have darkness, (A day absent or light)

Leon

[Brian W]

Leon, I tend to agree with you, no light = darkness but that would make darkness merely the absence of light. Which from a practical point of view makes sense. But is darkness in and of itself something?

[programmer]

What do you mean by 'no light'? Presumably the visibile spectrum. But what is 'dark' to our eyes is not so dark to those who might perceive light beyond our meagre limitations. It's not such a simple question.

[Brian W]

Well it is and it isn't an simple question. We turn out the lights its dark, we put on night vision goggles and we can see. But let me try it another way... The Big E was fascinated by light and its properties. Is it possible to be equally fascinated with 'dark' and find its properties or is it ultimately just a negation with no properties? Or would dark properties be the opposite of the properties of light?:shrug:

[MrB]

As far as I know(and I don't know much!), there are no dark particles/waves, therefore darkness is a lack of particles or waves that can be detected by any sensor.
And if a particle/wave can be detected, how could it be considered 'dark'?

Kind of like a perfect(and impossible?) vacuum, no particles = complete void = nothingness(is that a word?)
Like us... our bodies(actually, all bodies living or dead) are something just slightly short of 100% space. apparently some of the 'exotic' particles (Neutrino's?) can pass right through us and not hit a thing.

It's wierd thinking of nothingness, we tend to think that there must be something. Like the end of the universe thing.... It must end somewhere, but if it does, whats after the 'end'?
Is our 'bubble' universe just an atom in some other lifeforms body? Toenail for example?
And their universe an atom in..... hehe. Silly I know, but a thought I came up with when I was a teen. (I'm sure it's not original)

[skwinty]

We should first consider the definition of light.
ie information carried by photons (electromagnetic waves) in the visible spectrum that our eyes can detect.
The entire spectrum of electromagnetic waves cannot all be defined as light,
so if there is no "light" all we are saying is there are no Electromagnetic waves in that particular part of the spectrum.
So dark according to our definition doesn't imply that there are no other electromagnetic waves, just that we cant detect it with our eyes.
Even the big emptyness is full of energy, which is not visible, but can produce matter. mass equates to energy and vice cersa:thumbsup:

[Kevnool]

If you think the sky where you observe is very dark then whilst observing put your hand in the air and look at it, then you`ll see real darkness on your hand .....cheers Kev

[renormalised]

True darkness, as you have mentioned, would be a total absence of any radiation....visible or otherwise. But for an everyday definition of darkness, it's just the absence of visible light.

[Dujon]

Brian, your question reminds of one of mine, so many years ago, addressed to my science teacher of the day.

"If I block the light by using my right hand and then attempt to block the shadow by using my left hand, why doesn't the shadow get blocked?"

At the time it was a serious question to me - even though my fellow students laughed at me.

[Paddy]

Maybe the question could be rephrased. If there is no electromagnetic radiation (and no matter) you would just have space. Is space something? It can be bent, does this make it something even if it has no particles in order to "be" something?

[Brian W]

Paddy, that does begin to clarify the problem. If space can be bent, that means it can be manipulated. Which means that there is something there. The first question becomes how is 'it' measured? Considering that I have gone back to elementary school math to begin my math upgrade it is doubtful that I will be the one to find the answer or to formulate the question but it is interesting.
Brian

[Doug]

Brian for a truely insightful answer visit
http://home.netcom.com/~rogermw/darksuck.txt

cheers

[Brian W]

First gravity sucks and now light? of course this makes darkness a substance or the light bulb could never suck it in ! Eureka!

[AGarvin]

I think the correct answer to that would be "we don't know". The fact is we don't have a theory of space, and therefore can't say what it really is.



Actually, space is not really bent in the physical sense, but only within the mathematical framework of general relativity. GR uses the concept of curved space geometrically speaking, but that is to describe the effects of the presence of matter and energy on matter and energy, not on what space is physically doing.



There is a model of this type of universe (ie, no matter or radiation) called a de-Sitter universe (http://en.wikipedia.org/wiki/De_Sitter_universe), but like all models is developed from general relativity, and therefore still won't tell you what space actually is, just how the universe would evolve driven by a positive cosmological constant.

Of course all of this is deviating from the original post.

Andrew.